The present invention pertains to polishing compositions, and more particularly to polishing compositions for highly-filled resin-bonded dental restorations and nonprecious metal used in dental construction.
Materials used in dental restorations and dental construction must be polished in order to be acceptable to the dentist and the patient. Polished materials have a finished appearance and a smooth, natural feel in the mouth. Moreover, polished materials collect plaque less readily than unpolished materials and hence need cleaning less often. For these reasons it is desirable that materials used in dental restoration be polished. This polishing is generally accomplished in three steps, using successively finer abrading agents. The compositions of the invention are designed for use in the final polishing step, after the surface has been roughly finished and then prepared for polishing. The rough finishing may be accomplished with a number of commonly-available abrasive silicon carbide greenstones or carbide burrs as is well-known in the dental art. The second step, the finishing preparatory to polishing, may be accomplished with a number of commonly-available abrasive fine aluminum oxide whitestones and fine rubber-bound abrasive tools (e.g. a Dedco Tan Midget) as is well-known in the dental art.
Both highly-filled resin-bonded dental restorations and nonprecious metal dental constructions comprise a harder phase and a softer phase. In the former material, the quartz or other filler is much harder than the resin bonding agent; in the latter material, as disclosed for example in United States patent application Ser. No. 376,767, filed July 5, 1973, the nickel boride-chromium silicide included phase is harder than the surrounding nickel chromium matrix. Using prior art polishing compositions generally results in a more rapid abrading of the softer phase than of the harder phase to produce a "stepped" effect. That is, the resin is gouged out from between the quartz particle or the matrix is worn away more rapidly than the included phase. The resulting uneven surface is not polished. In order to have effective polishing there must be substantially equal abrasion of both phases of the material so that a smooth, even surface is produced.
Further, it is necessary to have efficient polishing, so that a dental technician or dentist can rapidly polish a nonprecious metal dental construction or a highly-filled resin-bonded dental restoration. Certain prior art pastes for polishing the former have been relatively effective polishing agents without being satisfactorally efficient. These pastes are unsatisfactory when compared with the pastes of the invention. It is also clear that the use of two or more pastes in the final polishing step is highly unsatisfactory because of the excessive amount of time necessary to polish using them.
The disadvantages of the prior art polishing compositions are obviated by the compositions of the present invention.